1. Field of the Invention
The present invention relates to novel compounds, N-[(1,2,3,4,5-pentaalkyl-2,4-cyclopentadien-1-yl)methyl]glycines, the preparation of the new compounds and their use as intermediates in the process for the manufacture of N-phosphonomethylglycine.
2. Description of the Related Art
By way of background, U.S. Pat. No. 3,799,758 describes N-phosphonomethylglycine and its use as an important herbicide. N-phosphonomethylglycine and derivatives thereof are effective herbicides at low rates of application when applied postemergence and are biodegradable into harmless residues within a relatively short period of time after their application.
Numerous processes for the preparation of N-phosphonomethylglycine have been disclosed in U.S. Pat. Nos. 4,053,505; 4,237,065; 4,415,503; 4,428,888; 4,946,993 and others. Most of these methods use glycinate esters or phosphinate esters, or both, which necessitate additional materials and reaction steps for their formation.
As reported in the literature, the typical Aza-Diels-Alder reaction between methylglycinate hydrochloride, formaldehyde and cyclopentadiene in water results in azanor-bornenes such as the azanorbornene methyl ester described by Paul A. Grieco et al., J. Am. Chem. Soc., 109:5859-5861 (1987). In U.S. Pat. No. 4,946,993, the method to prepare N-phosphonomethylglycine, which involves minimizing the quantity of water in the initial reaction mixture of glycine, formaldehyde and cyclopentadiene and adding the presence of an acid, similarly results in an azanorbornene intermediate.
One major disadvantage to the use of the azanorbornene intermediates in the process to make N-phosphonomethylglycine, however, is the undesirable by-products of the reaction, namely, certain polymeric materials which develop during the procedure. As a consequence of these tar-like substances, tedious purification steps are necessary to obtain the final product in suitable form for use in commercial formulations.
Due to the agronomic importance of N-phosphonomethylglycine, there is a need for improved methods of preparation utilizing new intermediates that are able to form the final product with less reactants and less reaction steps while able to eliminate the undesirable by-products of the azanorbornene reactions.